Geosynthetic material is used in a number of earthen supported constructions. Geosynthetic material generally refers to synthetic engineered products used in civil engineering projects including soil stabilization structures, corrosion barriers, retaining walls, abutments, and other earthworks requiring reinforcement. It has been found that geosynthetic material can offer a cost-effective and structurally sound alternative to many traditional concrete and block construction methods.
General types of geosynthetic materials include geotextiles or geotextile fabrics, geogrids, geomembranes, geosynthetic liners, geosynthetic erosion control products, and other specially designed geosynthetics. There are number of applications where geosynthetic materials may be employed, and the use of geosynthetic material applications is not limited to any particular field within civil engineering construction. Some of the more common functions that can be achieved with the use of geosynthetic material include erosion control, moisture control, drainage control, soil filtration and separation, soil reinforcement, and soil stabilization. One particular advantage provided by geosynthetic materials is that the materials provide substantial benefits in increasing both the tensile and shear strength of earthen supported structures. While concrete and block constructions may provide significant compressive strength, it is well known that these constructions can be woefully inadequate in terms of tensile and shear strength requirements.
Geosynthetic materials are commonly made from polymeric formulations, and another advantage of geosynthetic materials is that formulations can be adapted to achieve required strength specifications, and to otherwise be formulated for specific uses. With the wide range of polymeric materials available, geosynthetic uses continue to increase across many different types of construction applications.
One example of a reference that discloses a fiber-based geosynthetic material includes the U.S. Pat. No. 6,171,984. The reference also generally discloses geosynthetic composites with combinations of geosynthetic material including geotextiles fabrics and geomembranes.
U.S. Pat. No. 8,215,869 discloses a reinforced soil arch including alternating and interacting layers of compacted mineral soil and geosynthetic reinforcement material placed over and adjacent to the archway.
U.S. Pat. No. 6,890,127 discloses subsurface supports that may be used to support bridges and culverts, and more particularly, subsurface supports in the form of platforms that prevent scour type erosion that may develop from a body of moving water, such as a river or stream. The construction of the platforms includes the use of stabilizing sheet material, such as wire mesh, geosynthetic sheets, or combinations thereof.
U.S. Pat. No. 7,384,217 discloses a system and method for promoting vegetation growth on a steeply sloping surface. The system includes anchors secured to the sloping surface, an inner mesh layer in contact with the slope, a geosynthetic layer placed over the inner mesh layer, and seeded compost material placed in a gap or space between the geosynthetic layer and the inner mesh layer. And outer mesh layer is placed over the geosynthetic layer to stabilize the geosynthetic layer. Vegetation grows in the compost material, and roots of the vegetation penetrate the inner mesh layer into the slope for long term stabilization of the sloping surface to prevent erosion.
U.S. Pat. No. 6,808,339 discloses a modular retaining wall having tiers of headers which extend into compacted backfill material, and tiers of stretchers that extend between headers to form a front face of the wall. Layers of geosynthetic mesh reinforcement reinforce the load bearing capability of the backfill. Load forces in the backfill are sustained by forward ends of the layers of geosynthetic mesh reinforcement that extend upward in front of the backfill and then backward into the backfill instead of being sustained by the stretchers.
It is apparent from the wide variation in use of geosynthetic material disclosed in these references that geosynthetics can be used in multiple different types of constructions. Despite the increasing expansion in the use of geosynthetic material, there are still limitations in use of these materials. In the case of using geosynthetic material for larger scale construction projects, there is still a need to conduct on-site testing to confirm that the geosynthetic material in combination with the compacted earth formations achieve the necessary strength requirements for the particular project. Unlike concrete that may be tested in predictable and accurate small scale testing, such as slump testing, there is yet to be developed a uniform set of standards for determining how to employ geotextiles materials across various loading conditions.
Some efforts have been made to provide uniform guidance regarding employment of geotextile material. One example is the Geosynthetic Reinforced Soil Integrated Bridge System Interim Implementation Guide, published by the US Department of Transportation, Federal Highway Administration (June 2012). This reference generally discloses construction examples and preferred specifications for different types of constructions. This reference also discloses quality control and quality assurance measures, to include field testing and laboratory testing, and some guidance regarding stability analyses that may be conducted to confirm design specifications. However, this reference fails to disclose a testing method or procedure that can be used across many different types of construction projects to confirm actual performance of geosynthetically confined soils.
Because of the inherent number of variables with respect to use of geosynthetically confined soils, it has been difficult to develop a reliable and defensible mathematical equation that represents or predicts the behavior of soil and geosynthetic materials used in various constructions. For example, it is well known that the optimal compaction for soil greatly varies depending upon the type of soils encountered at a particular job site and therefore, designing and confirming a successful design using geosynthetics often requires trial and error testing at the jobsite in which soil and aggregate compaction is continually measured, and each lift of soil/aggregate must be tested multiple times to confirm optimal compaction. Further, the spacing of geotextile layers and a determination as to the number of layers used in a particular cross-section is not an established design sequence. Therefore, intense quality control is required at jobsite to ensure each lift of soil/aggregate material is properly compacted. Further, efforts have to be made to ensure that the soil/aggregate used at the jobsite is tested for optimal moisture content to ensure the type of soil and aggregate present can achieve its maximum dry density while the project is being constructed. Proctor compaction testing is yet another aspect of the construction process that can result with introduction of further variables for complicating design and implementation of a particular geostructural construction.
Therefore, it is apparent that a testing protocol or testing method is needed to enhance predictability of geostructural constructions, to not only reduce the potential for non-complying constructions, but also to reduce overall jobsite effort required for testing and quality control. There is also a need to provide a testing protocol and/or method that is easily transportable, and that can be quickly and efficiently conducted. There is yet a further need for a testing protocol/method in which deficiencies encountered regarding tested parameters can be retested and verified, thus preventing project delays and additional costs.